Biology is the study of life. It is a very broad discipline which includes key aspects of all the fields in the life sciences. Cell biology studies the function, ultrastructure and internal processes of cells of given organisms. Molecular biology examines these processes on the molecular level of proteins, DNA, RNA, etc.
Animal biology or zoology includes more specialized fields of study. Some examples are anatomy (structures), morphology (how shape or form relate to function), physiology (internal processes and functions and their coordination, genetics (heritability of the information that ultimately directs all life functions and responses to the environment), systematics and taxonomy (ordering, classifying and naming of species), evolution (origin and development of species), and ecology (interrelationships of living organisms with each other and the environment).
Human biology is an intensively studied area of animal biology.
Plant biology or botany is likewise divided into the same specialized fields of study found in zoology.
Microbiology includes the study of bacteria, viruses (virology), fungi (mycology) and protists, although many of the latter are studied in plant and animal biology. These component areas of microbiology may further subdivided into the fields of study mentioned above.